Disposing of vulcanized polymers represents a significant solid waste problem. Polymers that have been vulcanized have long been deemed as “permanent” or “irreversible”. This is due to the crosslinking of polymer chains, creating a rubber that no longer melts, but instead disintegrating at high temperatures.
One particular type of vulcanized polymer that presents a significant disposal problem is rubber tires. For instance, according to the California Integrated Waste Management Board Report, people in California wear out roughly 28 million tires per year. Across the country, there are altogether about 240 million old tires which are replaced each year. Commonly employed methods of disposal include incineration and discarding in landfills. Both approaches have significant problems. For instance, the incineration of rubber tires releases large quantities of pollutants, which inevitably increases the problem of air pollution in the region. Discarding of rubber tires in landfills is also problematic because they are not easily degradable, making them less than suitable for disposal in landfills.
Recently, ionic liquids have been explored for their potential use in recycling vulcanized polymers such as rubber tires. Ionic liquids are known for their nonvolatility and stability at high temperature making them suitable for consideration in a low emission recycling system.